Alloy Sheets Research Articles

Effects of Symmetric and Asymmetric Pre-Compression Combinations on the Mechanical Properties and Fatigue Behavior of ZK60 Magnesium Alloy

Pre-compression modes influence the microstructure of rolled magnesium alloys, thereby enhancing their mechanical and fatigue properties. This study investigates the distribution of dislocations, extension twins, and texture components in rolled ZK60 magnesium alloy sheets subjected to single-pass pre-compression (S-PT3), symmetric pre-compression (S-PT3R3), and asymmetric pre-compression (S-PT3R6). The results indicate that the variation in the orientation of pre-twin textures, leading to differences in the Schmid factor, is the primary cause of the mechanical performance differences observed under different pre-compression modes. In contrast, the hardening effect due to grain refinement is negligible. As the total amount of pre-compression increases, the hardening effect of pre-dislocations becomes more significant. Single-pass pre-compression exhibits a higher fatigue life under large strain amplitudes. Although asymmetric pre-compressed samples show increased overall strength and hardness, their fatigue life and cyclic stability are inferior. During cyclic loading, different pre-compression modes significantly impact the hysteresis curve, deformation mechanisms, stress ratio, and elastic limit amplitude. Symmetric pre-compression samples exhibit superior cyclic stability and fatigue life. Based on different application requirements, suitable pre-compression treatment methods can be selected to optimize the performance of ZK60 magnesium alloys, providing scientific guidance for practical engineering applications.

Effect of low velocity impact at different temperatures on hybrid adhesives in aluminium-composite single lap joints

This study aims to investigate the effect of a small stone impact on aluminum composite adhesive joints used in aircraft after exposure to various temperature conditions. In this context, single lap adhesive joints were prepared using 2024-T3 aluminium alloy sheets and 8-layer carbon fiber-reinforced epoxy hybrid composite sheets, with epoxy adhesive applied to the bonding surfaces. In addition, different types of hybrid adhesives were developed by reinforcing pure epoxy adhesive with various ratios (1%, 3% and 5% by weight) of graphene doped and undoped Nylon 6.6 (N6.6) nanofibers produced by electrospinning method to reduce brittleness. Low-velocity impact tests of 1.04 m/s under five different temperatures (−50, −20, 0, 23 and 50°C) were applied to all single lap adhesion joints produced and tensile tests were applied to the non-failed specimens to examine the loading conditions after low-speed impact. It was determined that approximately 1.5 J of the 3 J energy given by the low- velocity impact was absorbed in common in all samples, while the remaining part was returned and some separation occurred within the adhesion area due to the effect of this impact. While the low- velocity post-impact tensile strength of pure epoxy resin was measured as 2230.3 N at 23°C and 585.15 N at −50°C, the highest values were obtained in N6.6 reinforced epoxy adhesive with 1%GNP additive, which was measured as 3206.39 N at 23°C and 641.82 N at −50°C, and increased by 43.7% and 9.6% for 23°C and −50°C, respectively. In addition, the rupture surfaces of the specimens destroyed by the tensile test were examined by scanning electron microscopy (SEM) for damage analysis.

Optimization of bobbin tool friction stir welding parameters of AZ31 magnesium alloy based on FEM and its influence mechanism on mechanical properties

Based on the 3D transient heat transfer theory, the finite element model of bobbin tool friction stir welding (BT-FSW) of AZ31 magnesium alloy sheet is established. The effects of different process parameters on the quality of BT-FSW joint of magnesium alloy were discussed using temperature distribution, mechanical properties, fracture morphology analysis, and EDS element distribution analysis. The results show that in the process of BT-FSW, the cross-section temperature of the plate is symmetrically distributed in an hourglass shape, the AS is slightly lower than that of RS, and the transverse temperature is distributed in an ‘M’ shape. When the rotating speed is 700 rpm and the welding speed is 180 mm/min, the weld surface is smooth, and its ultimate tensile strength can reach 81.82% of the base metal strength. The tensile specimen is quasi-cleavage fracture. When the heat input is insufficient, there are a lot of Al8Mn5 Precipitated phases in the TMAZ fracture zone, which increases the fracture brittleness of the joint. When the heat input is enough, the precipitated phase dissolves evenly, the river-like fracture surface of the joint retains the dimple characteristics, and the mechanical properties are improved.

Numerical and Experimental Research of the Plastic Forming Process of Hastelloy X Alloy Sheets Using Elastomeric and Steel Tools

The results of experimental and numerical studies of plastic forming of sheets made of the difficult-to-deform Hastelloy X, a nickel-based alloy with a thickness of 1 mm, using layered elastomeric punches and steel dies, are presented in this publication. The elastomeric punches were characterized by hardness in the range of 50–90 Shore A, while the dies were made of 90MnCrV8 steel with a hardness of over 60 HRC. The principle of operating the stamping die was based on the Guerin method. The finite-element-based numerical modeling of the forming process for various configurations of polyurethane inserts was also carried out. The results obtained from numerical modeling were confirmed by the results of experimental tests. The drawpieces obtained through sheet forming were subjected to geometry tests using optical 3D scanning. The results confirmed that in the case of forming difficult-to-deform Hastelloy X, Ni-based alloy sheets, the hardness of the polyurethane inserts significantly affected the geometric quality of the obtained drawpieces. Significant nonuniform sheet metal deformations were also found, which may pose a problem in the process of designing forming tools and the technology of the plastic forming of Hastelloy X, Ni-based alloy sheets.

Bumps on metallographic specimens of Fe29%Ni18%Co alloy sheets as a rejection criterion

Bumps on metallographic specimens of Fe29%Ni18%Co alloy sheets as a rejection criterion

The influence of modification of the geometry of the front surface of the RFSSW tool inner sleeve on the fatigue life of joints during joining clad sheets made of aluminum alloy 2024-T3

AbstractRefill Friction Stir Spot Welding (RFSSW) has a number of advantages that make it a possible alternative to riveting and resistance welding in aerospace structures, the automotive industry and other applications. Adequate determination of technological parameters which ensure the desired properties of welds and their functioning in various operating conditions requires, among others, appropriate fatigue life of connections. The article presents the results of comparative tests of the mechanical properties of welds (load-bearing capacity and fatigue life at selected three load levels) made with a basic tool (G0) and a tool with a modified geometry (G4). The samples were made of 1.27 mm thick clad sheets of 2024-T3 aluminum alloy with an additional oxide anodic coating. It has been shown that the modified geometry of the working surface of the inner sleeve of the RFSSW tool improves the conditions and course of the plasticization and stirring process of the joined materials. The use of a G4 geometry tool allowed for approximately 30% higher joint load-bearing capacity and approximately twice as long fatigue life (at lower load levels) compared to welds made with the G0 tool.

Microstructural analysis of AA8079 alloy sheets formed by friction stir incremental forming

Friction Stir Incremental Forming (FSIF) is an innovative solid-state metal-forming technique that uses frictional heat and mechanical deformation to create complex shapes without dyes. It has found applications in industries like aerospace, automotive, and consumer goods. In this study, FSIF was applied to AA8079 alloy sheets to form cone and pyramid geometries. A detailed investigation of process parameters such as spindle speed, table feed, step size, and coatings was conducted to assess their effects on surface roughness and forming forces. Optimal parameters were identified using the Taguchi L27 orthogonal array and the TOPSIS method, which determined the best settings as a wall angle of 20°, a step size of 1 mm, a spindle speed of 1500 rpm, and a table feed of 2400 mm/min. Scanning electron microscopy was employed to study surface roughness, texture, and defects, revealing the influence of these parameters on surface quality. Additionally, Finite Element Method (FEM) analysis, performed using ABAQUS software, was used to predict formability and stress distribution during the forming process. Key results showed successful formation of cone and triangular pyramid shapes on AA8079 sheets, with FEM accurately predicting stress levels. This comprehensive study provides valuable insights into optimizing FSIF for improved material performance and structural integrity. The findings emphasize the importance of fine-tuning FSIF parameters to enhance surface finish and reduce defects, offering potential improvements for various industrial applications.

Deformation mechanisms of AZ31 Mg alloy sheet assisted by electrical pulse- ultrasonic composite energy field

Ultrasonic vibration and pulsed current can achieve energy concentration and effectively improve the forming ability of Magnesium alloy sheets. The uniaxial tensile tests of AZ31B sheets assisted by electric pulse, ultrasonic and electric pulse-ultrasonic composite energy fields were carried out, respectively. The influence of the effective current density and duration of the electric pulse on the softening, hardening and residual effects in the deformation process caused by the coupling action were explored. The electric pulse suppresses the promoting effect of ultrasonic vibration on twinning and together with ultrasonic vibration promotes dislocation slip to coordinate deformation. The composite energy field can thus further reduce the deformation resistance. The softening, secondary hardening and residual softening phenomena caused by the electric pulse-ultrasonic composite energy field become more and more significant with the prolongation of duration. When the ultrasonic field with a frequency of 21 kHz and an amplitude of 10 μm is combined with a frequency of 600 Hz and the effective current density increases from 0 to 30 A/mm2, the influence on the softening and secondary hardening process exhibits an initial increase followed by a decrease as the current density increases, while the influence on the residual softening shows the opposite trend.

Microstructure and mechanical properties of aluminum alloy laser welded joint assisted by alternating magnetic field

Magnetic field-assisted laser welding is an effective method to improve the quality of laser-welded joints. In this study, laser welding was conducted on a 2 mm thick sheet of 6061-T6 aluminum alloy, with the assistance of an alternating magnetic field oriented perpendicular to the surface of the sheet. The effects of the alternating magnetic field on the macrostructure, molten pool flow, porosity, grain morphology, and microhardness of the weld seam were analyzed. The results indicate that applying the alternating magnetic field results in more uniform and finer fish scale patterns on the upper surface of the weld. The porosity of the weld is significantly reduced. The Lorentz force generated by the alternating magnetic field suppresses liquid metal flow from the center to the edges of the molten pool, thereby hindering the heat flow and transfer within the pool. This concentration of heat in the lower part of the molten pool increases the size of equiaxed grains at the weld center and promotes the formation of more branches in the columnar grains near the fusion line. Some columnar grains in the columnar grain zone transform into equiaxed grains. Moreover, the microhardness distribution of the weld becomes more uniform, and the hardness in the heat-affected zone increases. Tensile tests revealed that all samples fractured within the weld seam, with the tensile strength of the welded joints increasing by 12.7%. The fracture mode transitions from a mixed ductile-brittle fracture to a purely ductile fracture.

Microstructure evolution and hydrogen absorption characteristics of gradient-hydrogenated Ti-4.5Al-3V-2Mo-2Fe alloys

Ti-4.5Al-3V-2Mo-2Fe rolled material is a dual-phase titanium alloy with an average grain size of less than 3 μm; its optimal superplastic forming temperature of 760 °C is at least 50 °C lower than the temperature required for diffusion bonding, making it challenging to carry out superplastic forming/diffusion bonding within a process window. The promotion of hydrogen on the low-temperature diffusion bonding of the alloy was verified through thermohydrogen processing, and the absorption characteristics of hydrogen in the alloy at various temperatures, holding times, and pressures were investigated. Subsequently, a mathematical model for achieving standardized hydrogen content was developed. X-ray polycrystalline diffractometer (XRD) analysis was utilized to preliminarily explore phase differences in samples with varying levels of hydrogen content. Furthermore, scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron back scatter diffraction (EBSD) and time of flight secondary ion mass spectrometry (TOF-SIMS) were employed to analyze microstructure changes and hydrogen distribution in both the surface and core regions of the titanium alloy following hydrogenation, demonstrating its feasibility for surface hydrogenation treatment of titanium alloy sheets

Dynamic optimization design of thin plate structure based on surrogate model

Abstract To enhance dynamic optimization efficiency in traditional thin plate structures, surrogate models are integrated for structural dynamic size optimization, reducing dependence on high-precision finite element simulations. This paper focuses on optimizing the aluminum alloy sheet as the subject of research. The parameters of the specimen are optimized through sensitivity analysis, based on the comparison between the free mode Finite Element Analysis (FEA) and Experimental Modal Analysis (EMA) results. The modified specimen undergoes validation under a four-edge clamped boundary condition. Subsequently, random vibration analysis is conducted to determine the root mean square (RMS) value of the acceleration response. Employing surrogate model technology, four models are constructed using parametric modeling and experimental design methods. These models are then compared for their fitting effectiveness. The results indicate that the RBF model exhibits the highest accuracy in fitting each response, effectively replacing dynamic simulation. Finally, the RBF combined with the NSGA-II method, optimizes the specimen’s structural size, resulting in a 21.6% reduction in mass and an 18.60% decrease in acceleration response. These outcomes demonstrate satisfactory optimization results, ensuring accuracy while enhancing the dynamic characteristics of the specimen structure. This research offers valuable insights for related engineering applications.

Enhancing corrosion resistance of Al alloy sheets with potential gradient by arc-sprayed Zn coatings

To improve the corrosion resistance and wide the application of Al alloy sheet in the engineering production, a corrosion potential gradient along the thickness of the Al alloy sheet was fabricated using the sprayed Zn layer. The process of arc spraying was employed to obtain the Zn coating with optimizing the parameters. Electrochemical testing was conducted on the surface of Al alloy sprayed with Zn layers at different depths. As the depth in the thickness direction increases, the content of Zn alloy elements gradually decreases and the potential gradually increases. This exhibits a gradual decrease in corrosion tendency. The results of electrochemical impedance spectra (EIS) revealed the existence of pitting corrosion on the surface of the Al alloy. This even extended to the underlying substrate material. In contrast, the Zn coating, when exposed to a corrosive environment, demonstrated the beneficial cathodic effect as a sacrificial anode and the protective function of a passivating film, thus mitigating corrosion. The gradual increase in charge transfer resistance in the impedance spectrum suggested that the corrosion resistance of the sample is increasingly improved. Therefore, it exhibited remarkable resistance to corrosion. Additionally, the SEM surface morphology and XRD pattern were utilized to further explain the corrosion mechanism of the arc-sprayed Zn coating. The Zn coating can provide sacrificial protection to the Al layer due to its higher negative potential and localized corrosion reactivity. This is attributed to the micro-galvanic couples formed between the Zn and Al layer, thus increasing the corrosion resistance of the sheets.

Microstructure Evolution and Mechanical Properties of Pure Ti Alloy Sheet Fabricated by Double-Side Corrugated Rolling

Microstructure Evolution and Mechanical Properties of Pure Ti Alloy Sheet Fabricated by Double-Side Corrugated Rolling

Effect of Pulse Current on Friction Coefficient of 7075-T6 Aluminum Alloy and Microstructure Analysis

Abstract A study on friction is necessary to improve the forming quality of stamped parts. It has been found that pulsed current can improve the forming properties of aluminum alloys, mainly in terms of Joule heat and electroplasticity. Thus, this article revolves around the effect of different current densities on the friction and wear of 7075-T6 aluminum alloy sheets. The change rule of friction coefficient under different current densities is derived through a friction test, and the variable friction simulation model is established. Scanning electron microscope (SEM) and X-ray diffraction (XRD) are used to analyze the micromorphology and elemental composition of the wear surface. The diffraction peaks of Al are analyzed by XRD, and grain size and dislocation density are calculated. Finally, the actual stamping results are compared with the simulation results. The results show that the friction coefficient decreases with the increase of current density when the current density is less than 10 A/mm2, and the wear mechanism is mainly abrasive wear. When the current density is greater than 10 A/mm2, the friction coefficient increases with the increase of current density and the wear mechanism is mainly adhesive and electrical wear. The grain size and dislocation density mainly depend on the electrical plasticity. The variable friction model's simulated thickness distribution and rebound results align more with the situation.

The Influence of As-Cast Grain Size on the Formation of Recrystallized Grains and the Related Mechanical Properties in Al-Zn-Mg-Cu-Based Alloy Sheets.

The influence of as-cast grain size on recrystallization and the related mechanical properties of Al-Zn-Mg-Cu-based alloys was investigated. Grain sizes ranging from 163 to 26 μm were achieved by adding Ti, Cr and Mn, and ZnO nano-particles, which acted as heterogeneous nucleation sites. A decrease in the as-cast grain size led to a corresponding reduction in the recrystallized grain size from 54 to 13 μm. Notably, as-cast grain sizes below 100 μm provided additional nucleation sites at grain boundaries, allowing for a reasonable prediction of recrystallized grain size. Finer grains also contributed to enhanced mechanical properties, with yield strength increasing as recrystallized grain size decreased without significant loss of elongation. Additional strengthening was observed due to η-precipitates at grain boundaries, further improving the properties of fine-grained sheets.

Mechanical performance of dissimilar Al6082 aluminum and AZ91 magnesium alloy joints produced by friction stir welding

Abstract The current research work aims to produce a defect free joint of Al6082 aluminum and AZ91 magnesium alloy sheets by friction stir welding (FSW) at various tool rotational and travel speeds with an objective to obtain the best combination of welding parameters to produce quality joint. The weld joint that was produced at the combination of 1400 rpm tool rotational speed and 30 mm min−1 feed exhibited defect free stir zone. Microstructural studies carried out in the weld joint demonstrated mechanical mixing of base materials from both the alloys in the stir zone. The mixing of Al6082 and AZ91 alloys was clearly appeared in the weld zone. It can be observed that the x-ray diffraction studies clearly demonstrated the development of intermetallics in the weld region. Higher hardness was observed for the joints that can be ascertained to the presence of more mixed regions in the stir zone that contains hard and brittle intermetallics. From the tensile test data, lower strength (175.71 ± 4.24 MPa) was observed for the weld joint compared with Al6082 (242. 6 ± 11.4 MPa) and AZ91 (205.27 ± 6.39 MPa) base materials. Furthermore, the ductility of the weld joint was measured as marginally higher than the AZ91 Mg alloy and lower than the Al6082 alloy. It can be concluded that the defect free weld joints of Al6082-AZ91 alloys can be successfully produced by FSW for structural applications targeted for dry environment.

Elucidating the effect of strain path-dependent crystallographic texture evolution on the electrochemical behavior of nanostructured AA2024 aluminum alloy

This research provides insight into the effect of strain path-dependent texture evolution on the electrochemical behavior of nanostructured AA2024 aluminum alloy in a phosphate buffer solution (pH = 8.3). To achieve this, AA2024 alloy sheets were processed using two methods: accumulative roll bonding (ARB) and cross accumulative roll bonding (CARB), i.e., rotating the sheets 90° around the normal direction (ND) axis between each cycle. The ARB-processed AA2024 alloy exhibited a pancake-shaped structure and included texture components of Copper {112}<111>, Brass {011}<211>, P {110}<221>, and S {123}<634>. Meanwhile, the CARB-processed AA2024 alloy had extremely fine and equiaxed nano-grains (< 100 nm) and texture components of S {123}<634>, Brass {011}<211>, Goss {011}<100>, Rotated Cube {001}<110>, and P {110}<221> after eight cycles. Electrochemical studies demonstrated an increase in corrosion current density due to high imposed strains in the ARB route, which in effect made the conditions of passive layer formation more difficult and lowered the corrosion resistance. Additionally, achieving a more uniform distribution of extremely fine grains and {011} orientation textures such as Brass {011}<211>, Goss {011}<100>, and P {110}<221> texture components in the CARB route, provided ideal conditions for forming oxide passive films with superior protection properties compared to ARB. These unique findings can contribute to the broader application of crystallographic-orientation-dependent electrochemical behavior of alloys in the field of corrosion management.

Investigating formability of AZ31B magnesium alloy sheet with different texture and thickness in combination of the Erichsen experiment and CPFEM model

In this study, the formability of the AZ31B magnesium alloy sheets was investigated in combination of experiment and CPFEM modelling. The deformation mechanisms during the Erichsen forming were revealed and the effect of the related parameters were discussed. It was shown that the simulation results based on the normalized Cockcroft-Latham criterion are consistent with the experimental results. The maximum stress and strain concentrate at the center of dome, and exhibit an elliptical distribution shape. The difference of asymmetry situation between the sheets results from the different textures. The basal <a> slip is the dominant mode, and the prismatic <a> slip is also active to accommodate plastic strain in sheet plane. The relative activity of the pyramidal <c+a> slip is low, but very effective to accommodate the plastic strain in thickness direction. The sheet with higher relative activity of the prismatic <a> and pyramidal <c+a> slips exhibit higher formability. The sheet thickness influences the formability through changing the stress-strain response, as well as the orientation-relationship between stress state and grains which can affect the deformation mechanisms. The formability depends on the plastic strain accommodation ability that is comprehensively related to the averaged plasticity, orientation-relationship between stress state and grains, r-value and n-value. CPFEM modeling is convenient pathway to predict the formability.

Design of flat hole-clinching for joining polymer and metal sheets

There is a growing need for joining processes capable of joining dissimilar materials, specifically lightweight materials. In this study, flat hole-clinching (FHC) is developed for joining polycarbonate and AZ31 magnesium alloy sheets. A ductile fracture criterion is calibrated using tensile tests and employed in the finite element analysis of the process to investigate the effect of geometric parameters on the joint characteristics and strength. A tool concept is also proposed for the FHC process. Results show that the FHC process enables to successfully connect these sheets without fracture. The flat hole-clinched joint resisted the maximum force of 0.9 kN in the pull-out test, and failed with bottom separation mode.

Effect of Ca addition on structure, phase composition and hardness of Al–6 %Cu–2 %Mn sheet alloy

The Al–Cu–Mn–Ca system was proposed as a bases for the design of new group of heat-resistant alloys which can be used for high-temperature applications instead of the 2219 types industrial alloys. Unlike the latter ones, the new alloys also do not require a full cycle of strengthening heat treatment including solid solution treatment, quenching and aging. The effect of calcium addition in the 1–4 wt% range on the structure, phase composition and hardness after high temperature annealing of the Al–6 %Cu–2 %Mn base sheet alloy has been studied. It has been shown that calcium addition leads to the formation of high-temperature eutectics (614–617 °С) with the participation of the Al27Ca3Cu7 and (Al,Cu)4Ca phases that are capable of spheroidization at high temperature annealing. The ingots of Ca-containing alloys do not require homogenization but have sufficient deformation plasticity at both hot and cold rolling. The structure of the previously unstudied quaternary Al–Cu–Mn–Ca phase diagram in the region of the aluminum corner has been also proposed, according to which it can contain 5 four-phase fields in the solid state with the participation of (Al), binary (Al2Cu, Al4Ca, Al6Mn) and ternary (Al8CaCu4, Al27Ca3Cu7, Al10CaMn2 and Al20Cu2Mn3) phases. Based on the obtained data, the composition Al–6 %Cu–2 %Mn–1 %Ca has been proposed as a basis for the development of a new heat-resistant alloy. It is shown that this alloy superior to industrial 2219 alloy in terms of heat resistance, especially after annealing at 400 °C, when the difference in hardness reaches 32 HV. The high heat resistance of the new wrought alloy originates from the formation of a specific microstructure consisting of fine Ca-containing eutectic inclusions and Al20Cu2Mn3 phase dispersoids with a size of about 100 nm which prevent recrystallization and allow maintaining the fine sub-grained structure.